code: def test_fp64(self):
      x = (
          numpy.zeros((1, 2, 3), dtype=numpy.float64),
          numpy.zeros((1, 2, 3), dtype=numpy.float64),
      )
      f = F()
      y = f.apply(x)
      assert f.x[0] is x[0]
      assert f.x[1] is x[1]
      assert y[0].dtype == numpy.float64
      assert y[1].dtype == numpy.float64
  
file_path: chainer/tests/chainer_tests/utils_tests/test_precision.py
imports: import unittest
  import numpy
  from chainer import function_node
  from chainer import testing
  from chainer.utils import precision
label_desc: Use image node_id 3 for calling the TestMixedPrecision obj's underlying member method code with example usage: obj.test_fp64() without return types